1. Field of the Invention
The present invention relates to valves having rotatable valve elements and, more specifically, to an assembly for rotating and positioning the valve element of a rotatable valve.
2. Description of the Prior Art
Rotatable valves such as butterfly or disk valves, ball valves, plug valves, etc. are commonly provided with a valve stem which is attached to the valve element and which protrudes out of the valve body whereby the valve element may be rotated or positioned, externally of the valve body, by turning the valve stem. The valve stem may be rotated either manually by the use of a handle attached to the valve stem or automatically using an actuator assembly attached to the valve stem. In either event, the valve stem is provided with wrench flats or some other engagement means by which a handle, actuator or the like can be removably attached to the valve stem to prevent relative rotation therebetween.
It is quite common, particularly in the case of valves which are used in lower pressure applications, to utilize a handle whereby the valve can be manually operated. In order that the valve element may be rotated to a desired open position, e.g. in a throttling position, it is common for a positioning or indexing plate to be attached to the body and which is operatively associated with a latching mechanism on the handle such that the position of the handle and hence the position of the valve element can be selectively, releasably locked in a desired position.
Prior art handles for use with butterfly valves, ball valves, etc. are expensive to manufacture, both in terms of amount of material required and in machining operations, generally require expensive and time consuming casting or forging operations and are bulky. For example, a typical prior art valve handle is made from a casting and includes a broached sleeve which has wrench surfaces to engage the wrench flats of the valve stem. Additionally, the handle is provided with a pivotable, spring biased detent as a latch which is used to engage a notched plate (positioning plate) secured to the body of the valve, generally to the flange on the neck, such that the valve element can be moved to a desired position and maintained in that position by engagement between the detent and one of the selected notches on the plate.